For complete confidence that your guitar is getting the humidification it needs in dry seasons without worrying about your humidfier leaking or hurting your instrument, check out the original blue Oasis® guitar humidifier. The OH-1 guitar humidifier is a soundhole humidifier designed to maintain 45-55% relative humidity inside the guitar body when the humidity outside the case is between 25-40%, provided that the guitar is already hydrated.